Database BASIC REAL AND COMPLEX FUNCTIONS Basic trigonometry The natural logarithm on complex numbers logimcld  
				
		 
		
			
		 
		Description:   The imaginary part of the logarithm is in ( -upi (,]  pi )  .
       Deduction form of logimcl  .  Compare logimclad  .  (Contributed by David Moews , 28-Feb-2017) 
		
			
				
					Ref 
					Expression 
				 
					
						Hypotheses 
						logimcld.1 ⊢  ( 𝜑   →  𝑋   ∈  ℂ )  
					
						logimcld.2 ⊢  ( 𝜑   →  𝑋   ≠  0 )  
				
					Assertion 
					logimcld ⊢   ( 𝜑   →  ( - π  <  ( ℑ ‘ ( log ‘ 𝑋  ) )  ∧  ( ℑ ‘ ( log ‘ 𝑋  ) )  ≤  π ) )  
			
		 
		
				Proof 
				
					
						Step 
						Hyp 
						Ref 
						Expression 
					 
						
							1 
								
							 
							logimcld.1 ⊢  ( 𝜑   →  𝑋   ∈  ℂ )  
						
							2 
								
							 
							logimcld.2 ⊢  ( 𝜑   →  𝑋   ≠  0 )  
						
							3 
								
							 
							logimcl ⊢  ( ( 𝑋   ∈  ℂ  ∧  𝑋   ≠  0 )  →  ( - π  <  ( ℑ ‘ ( log ‘ 𝑋  ) )  ∧  ( ℑ ‘ ( log ‘ 𝑋  ) )  ≤  π ) )  
						
							4 
								1  2  3 
							 
							syl2anc ⊢  ( 𝜑   →  ( - π  <  ( ℑ ‘ ( log ‘ 𝑋  ) )  ∧  ( ℑ ‘ ( log ‘ 𝑋  ) )  ≤  π ) )